We just moved to Hudson 1.368 from 1.348, and now the Netbeans "Hudson Builders" Services cannot connect and track the status reporting an error like "Provide a valid Hudson root URL (1.291 or newer)".
Hudson does work fine, the webpage is accessible, and we can see an answer being set to the NB client when monitoring with wireshark.
Platforms involved: Netbeans 6.9 client, Hudson 1.368 under tomcat 6.0.24 (on OpenSUSE 11.3)

Reproducible (with a dev version of NB too, it does not matter). Seems this version of Hudson is missing a crucial header field (see URL for upstream bug). Use 1.367 until a fix can be released, I hope in 1.369.